Dzień dobry!

Dzień dobry!

Greetings from Poland! Czy mówisz po polsku? Do you speak Polish?

This summer Katie Lee and Mary Rogers (that’s us!) from LEE are doing field work in Southern Poland. We will have a few blog posts over the summer about our experiences.

Jedziemy do Polski!  

Poland was chosen as our field site for a variety of reasons. Our badania (research) asks questions about life experiences and reproductive health. The area of Poland in which we are recruiting study participants is a more rural environment. The majority of the population breastfeeds longer than the average American, many people don’t use hormonal contraception, physical activity levels are higher, and eating habits are different. This population provides an interesting comparison to urban populations where most people have an energy surplus as sedentary activity is more common and food resources are easily available.

To get to Poland we flew through multiple airports. We left our home airport at noon on Friday and arrived in Krakow on Saturday mid-morning. Apart from a bit of jet lag, we had a fun time walking around in Krakow on Saturday – we visited Wawel Castle and walked around the centrum. We also tried to purchase any last-minute supplies for our fieldwork before we left on Sunday morning.  It was surprisingly difficult to shop for supplies when you can’t connect the name of a store with the type of product it might sell!  To add to the difficulty, many types of packaging are different here. For example, juice and milk are NOT found in the refrigerated section because they are in shelf-stable cartons.

On Sunday we left Krakow with our collaborators from Jagellonian University to head to our Mogielica field site in a van FULL of supplies and equipment. The curvy road and fast cars were at times a bit nauseating, but we made it to our awesome home-away-from-home in one piece. 

Van full of lots of equipment, supplies, luggage, and us.

Kate and Katie outside our new home-away-from-home. 
We have the top two floors for all of the research team and supplies.

Nie rozumiem, and other useful phrases

Living in a new city without knowing the language well has been quite difficult. It’s hard to do the easy things that we, as English-speakers, take for granted in English-speaking countries. For example, every trip to the store has been an adventure! We’ve been fairly successful figuring out what words mean by the pictures. “Ser” means cheese, and, wow, there are a lot of delicious types of cheeses here! Spreadable garlicky cheese, local farmer’s cheese (like goat cheese)… it is so delicious!

One of our adventures in language-learning included a day dedicated to finding a bus to Limanowa. We found a bus stop, but we also knew that there was another bus stop up the hill. We decided to go into a sklep (a shop) and ask for help. With our basic Polish words, we were able to ask where the bus for Limanowa could be found, and, as it turns out, we had gone to the right one! There was no timetable, so we just waited until a bus showed up.  The bus was much smaller than most buses in the US, and you have to open the door yourself with a handle, similar to a car door.  We had the next language difficulty of asking how much the bus would cost. After a few unsuccessful attempts, we got a phrase correct and learned that the bus costs 3 złoty. We successfully made the trip to Limanowa!

We were successful getting on the autobus!

However, once we got to Limanowa we were in for a bit of a surprise. Most of the shops and attractions had closed at 2 or 3 PM! We just walked around a little bit, and then decided to take a bus back home. We found a timetable this time, only to discover that there was just one more bus! Our purpose of the trip was to buy more research supplies, which we hadn’t been able to complete. We decided to go to one more shop and risk missing the last bus. We got our supplies, but, unfortunately, we missed the bus. It was a bit of a hike back, but our walk allowed us the opportunity to see more of Poland. Now we also know that if we want to do something fun on Saturday in Limanowa, we should go early!

Settling in

We are settling in to the field site and getting used to the rhythms of fieldwork and meal times.  Our collaborators have been very understanding about our limited Polish language skills and incredibly patient when they try to teach us new words.  The people who own the house we rent let us eat some food from their garden and have introduced us to some of their local family members.  Despite their rusty English and our stilted Polish, we can have a surprisingly good conversation.  As an additional highlight, we have friendly dogs at our house who greet us when we walk out the door and when we return from a long day walking the Polish countryside. 

Our dog loves Katie!

LabEvoEndo Journal Club: Dana Ahern presents on PMDD

This is the third guest post of the LabEvoEndo Journal Club, a new series for the LabEvoEndo blog meant to highlight student contributions to the lab (first post here, second post here). The author is Honors Anthropology Junior Dana Ahern. Dana has been in my lab since her sophomore year.


* * *
I’d like to start this blog post with a little background on progesterone. Progesterone is fascinating and it affects a lot more than just the menstrual cycle. We are starting to understand just how big of an impact progesterone has, and the research project I am working on is beginning to show some of the potential applications of progesterone in medicine. These applications include improving recovery time after traumatic brain injury and strokes, as well as helping us understand postpartum depression (PPD) and premenstrual dysphoric disorder (PMDD).

PMDD is similar in mechanism with postpartum depression, although the exact mechanism is still being researched. Some research suggests a hormonal influence, as allopregnanolone, an offshoot neuroregulator of progesterone, modulates GABA, which is a neurotransmitter related to mood and anxiety. Too much GABA results in increased anxiety and mood related issues, so it is a logical conclusion that the drop in progesterone during the late luteal phase of the menstrual cycle would result in excess GABA and therefore symptoms of PMDD.

The article we discussed looked at PET scans of 12 women with and 12 women without a diagnosis of PMDD, taking scans during the follicular phase and the late luteal phase of their menstrual cycles. The women in the study were screened for two months with mood surveys and then taken in for a day of PET scans and blood/urine samples, once during the follicular phase and once during the late luteal phase, when the symptoms of PMDD would have begun. PMDD can affect certain brain functions, so they were using the PET scan to detect brain dysfunction, such as one study the article looked at that showed frontal lobe dysfunction associated with PMDD.

The hormone measurements didn’t show anything significant and PET scans showed increased cerebellum activity from follicular to late luteal phase in PMDD women only. The cerebellum has many GABA receptors, which is a possible explanation of this, but in journal club, we wondered if it is the lack of modulation after a drop in the progesterone, or if there is something going on with the number of receptors, such as perhaps some sort of diminished sensitivity to allopregnanolone.

In journal club, we discussed some of the problems we had with this study. Someone brought up the small sample size and too few collection times for samples and scan. The fact that only one cycle was measured impacted the study. Kate also mentioned that blood hormones are a less useful measure than salivary hormone measurements. Finally, while the article states that the cause of PMDD is an overactive cerebellum in women suffering from PMDD, they never really reach a definite reason for what is causing the increased action. Ultimately, the article would have benefitted from examining the hormones more closely and more often.

Reference

Rapkin AJ, Berman SM, Mandelkern MA, Silverman DH, Morgan M, & London ED (2011). Neuroimaging evidence of cerebellar involvement in premenstrual dysphoric disorder. Biological psychiatry, 69 (4), 374-80 PMID: 21092938

LabEvoEndo Journal Club: Sophia Bodnar presents on cervical cancer

This is the second guest post of the LabEvoEndo Journal Club, a new series for the LabEvoEndo blog meant to highlight student contributions to the lab (first post here). The author is Anthropology Junior Sophia Bodnar. Sophia has been in my lab since her sophomore year.

* * *
In light of recent acceptance to a summer program where I will be working in immunology, I wanted to choose an article relevant to reproductive health and immunology. The first place I turned to was the Journal of Reproductive Immunology. This seems like a copout, but I found a very interesting and recent article for the lab meeting entitled "Higher levels of cervicovaginal inflammatory and regulatory cytokines and chemokines in healthy young women with immature cervical epithelium" by Hwang et al in 2011.

It would be wonderful if human variation was always taken into account, particularly when discussing reproductive health. This is exactly what the researchers from UCSF aimed to do and why this article was a refreshing read. It is known that women aged 15-24 have the highest rates of Sexually Transmitted Infections (STIs) and is commonplace in the medical community to associate STIs with risky sexual behavior. The study looked at cervical epithelium, tissue that lines the cervix, and accompanying levels of cytokines and chemokines in order to show basic biological differences in immune function of the cervix between adults and adolescents to account for the predominance of STIs in younger women.

Thirty-two women aged 13-21 were selected. The women were placed in the immature group (>50% columnar epithelium) or mature cervical group (<5% columnar epithelium). In order to help you envision these epithelial cells, think of a single line of figure skaters (fragile, columnar cells) versus a stack of sumo wrestlers (strong, squamous cells). Younger women have more columnar cells and throughout development the columnar cells become squamous cells. This is why it is extremely important to take variation into account, because at any given point in a woman’s development the ratio of squamous to columnar cells varies.

Participants were excluded for pregnancy, surgery on the cervix, cervical dysplasia (grades above 1), taking immunosuppressive agents, or being symptomatic for genital complaints such as yeast. However, women were not excluded for having HPV because the researchers consider it a very common infection. The women filled out surveys detailing sexual and nonsexual behavior (number of partners, contraception, substance abuse, etc) and reproductive health history (previous pregnancies, menarche, etc). Colpophotagraphs were taken of the cervical epithelium and the researchers measured and rated maturity by counting pixels from the photograph. Women were evaluated only once, a strong drawback to this study as they are interested in the variation of the epithelium.

They found that ten of the cytokines and chemokine levels were higher in the immature group (one cytokine was excluded). Although other studies have previously looked at cervical levels of cytokines and chemokines, this study looked at levels of these cell-signaling protein molecules in relation to type of cervical epithelium. The authors note that having more columnar cells may be considered beneficial for young women as these cells are more easily damaged and likely to initiate an immune response, but this would mean that younger women are less prone toward infection. The researchers then go on to conclude that because these columnar cells are more prone to damage and thus immune response, chronic inflammation is more likely which could lead to greater rates of infection. This study only looked at the epithelium of healthy women, so it is important to examine women with various infections in the future. The epithelium and levels of cytokines/chemokines in women with STIs could lead to a better understanding or correlation between type of epithelium and its subsequent immune response and risk rate.

In our discussion of the article, it was mentioned that there are no “normal” levels of cytokine and chemokine levels with which to compare the researcher’s values. In the study this was referred to as a challenge. Perhaps there will never be established normative levels of these protein molecules, but so what? Our lab group concluded that this should not be considered a challenge and may be beneficial as we will simply have to take variation into account which is strongly lacking in the medical realm of reproductive health! We all agreed that this study should have been conducted over a longer period of time, and that the women should have had their epithelium photographed and correlating levels of cytokines/chemokines measured far more often. Because this study’s main focus was variation of the epithilium, it would make sense for these women to contribute visits over the course of their entire menstrual cycle whereas this study simply adjusted for days since last menstrual cycle. We also discussed that this study may be perceived as far more qualitative than quantitative. However, we acknowledged that the clarity of the cervical photos was great so quantitative measurements of the pixels could be taken seriously. It was also noted that these findings were not all that surprising. It seems commonsense that younger women have cells that are more easily damaged and that this could lead to chronic inflammation that poses negative risks. Although this may be true, I think that we should still applaud these authors for acknowledging variation throughout their research.

I also find it interesting that the most common cervical cancer is squamous cell carcinoma. Columnar cells may be damaged more easily, but it seems that squamous cells are more prone towards division and supporting abnormal growth. Most cases of cervical cancer are due in part to HPV infection, which in going along with the findings of this article, is more common in younger women with immature columnar cells. It would be interesting to see how the squamous cells in women with cervical cancer compare to the columnar cells of women with HPV. Perhaps cervical cancer, as a result of HPV, is more common in women who have more columnar cells than squamous cells, but the cancer arises in and prefers the squamous cells because they are less likely to initiate a strong immune response. In general, I appreciate how easy and enjoyable this article is to read. Hopefully more articles acknowledging variation, particularly when it comes to reproductive health, will be published as a result of this interesting finding.

Reference

Hwang LY, Scott ME, Ma Y, & Moscicki AB (2011). Higher levels of cervicovaginal inflammatory and regulatory cytokines and chemokines in healthy young women with immature cervical epithelium. Journal of reproductive immunology, 88 (1), 66-71 PMID: 21051089

LabEvoEndo Journal Club: Laura Klein presents on food allergies

This semester I'm trying out something a bit new -- I've encouraged my students to do quick write-ups of the papers they present in journal club in a way they think would be suitable for a blog post. This is to share what we're up to and give my brilliant students a chance to show their stuff.

This first guest post of the LabEvoEndo Journal Club is by Integrative Biology Honors Senior Laura Klein. Laura's been in my lab since her sophomore year.


* * *
Welcome, readers! This blog post will start a series of posts by undergraduate lab members about the topics that LabEvoEndo currently finds interesting and are discussing in our weekly lab meetings. Usually, these will be related to our own current research projects and will somehow tie into the broader goals of the lab.

The other week, I spent a lot of time looking at some Polish survey data related to food allergies and food intolerances that Dr. Clancy and I collected last summer. This led me to thinking about the health implications of food allergies, so this week’s lab meeting article is "Food allergies in children affect nutrient intake and growth” by Christie et al from 2002. As the authors from this article are all medical professionals, I also wanted to supplement this article with some information about the daily social stressors that food allergies can have on individuals or families, so we also read excerpts about The Impacts of Food Allergies on the Quality of Life’ from Fernandez-Rivas and Miles “Food allergies: clinical and psychosocial perspectives.”

To give you some background for the study, 6-8% of American children will develop food allergies in the first 3 years of life, which also happens to be a critical period for growth. Of children with food allergies, most will have a single allergy to cow’s milk, eggs, peanuts, what, soy, tree nuts, or fish. Previous studies have found that children with cow’s milk allergies have a lower height/age ratio, though they did not propose a mechanism for this trend. One possibility is that elimination diets in general may reduce the amount of macro or micro nutrients available in the diet.

In this study, Christie et al. compared 98 children with and 99 children without food allergies (all about age 4) to determine if food allergies and elimination diets impact the growth and nutrient intake of children with food allergies. All children who were diagnosed with an allergy had been following a food elimination diet. The BMI, height-for-age, and weight-for-age for all children was compared to the CDC’s Health Statistics Growth Charts, and individuals were classified as having ‘potential undernutrition’ (<25th percentile), ‘adequate nutrition’ (25th-75th percentile), and ‘potential overnutrition’ (>75th percentile). Parents also completed three days of dietary intake records, which were compared with recommended dietary allowances.

The authors found that more children with allergies were categorized as having ‘potential undernutrition’ as determined by height-for-age than children without allergies. Additionally, a large number of these children had two or more allergies. Because the article only focused on height-for-age despite collecting many other measurements, we were skeptical that food allergies were the sole cause having low height-for-age. Some possibilities that we discussed but the study did not control for included premature birth and genetic influences on height or growth rates.

Another study result that generated much discussion was that more than 25% of the children in both the control and allergy groups were not getting the recommended daily intake levels of calcium and Vitamins D & E. We thought this was problematic, not necessarily for the health of the children, but for how recommended daily intake levels are defined. Children with milk allergies who consumed supplementary fortified beverages were more likely to be meeting all of the intake recommendations than even children without any dietary restrictions. Considering this, are the current guidelines a reflection of realistic intake for small children?

In the discussion, the authors introduce the possibility that ‘catch-up’ growth during puberty. They suggest that this could be many food allergies disappear as children mature, so foods can be reintroduced into the diet. However, we also suggested that early teenagers are usually simply hungrier than toddlers (as anyone who has been in a high school cafeteria knows). Greater consumption of calories may provide greater energy sources for growth. Also, by puberty, people usually have more access to food because they are able to prepare it themselves. Both of these situations could contribute to more available energy that could be used for growth.

Finally, we wrapped up our discussion talking about how different kinds of elimination diets have biological and social impacts. For members of our group with food allergies and intolerances, especially ones like nuts or gluten, group dinners can be a challenge because hosts can be unsure what to prepare and may only have one or two ‘safe’ dishes. This related to a problem brought up in both articles- that parents with children newly diagnosed with food allergies may unnecessarily restrict many foods because they are unsure what will cause an allergic reaction. This could cause an artificially limited availability or nutrients or calories. And, to tie this back to an earlier point, as children grow up and learn what foods to avoid, their teachers and friends’ parents may give them more freedom to choose a range of foods that are acceptable, instead of limiting them to one or two ‘safe’ foods.

A good analogy to this situation might be someone who has just decided to adopt a vegetarian diet. Younger people may at first be so focused on avoiding meat that they don’t pay attention to the nutrition content of their food. For example, cheese pizza and grilled cheese are meat-free, but don’t provide all protein, vitamins, and minerals needed for a complete diet. Also, young people who still live at home may have less control over the types of food bought or prepared. As one former vegetarian in the group told us, to balance all the portions of your diet takes a lot of effort and planning. She said she had never been more aware of what she was eating, but that it took time to figure out how to achieve a good balance of nutrients.

Stay tuned for updates and about brains and hormones!

References

Christie L, Hine RJ, Parker JG, & Burks W (2002). Food allergies in children affect nutrient intake and growth. Journal of the American Dietetic Association, 102 (11), 1648-51 PMID: 12449289

Fernandez-Rivas, M, & Miles, S (2007). Chapter 1. Food allergies: Clinical and Psychosocial Perspectives Plant Food Allergens DOI: 10.1002/9780470995174.ch1

Adolescent Menstrual Variation and Oral Contraceptives

The guest post below is by LEE alums Theresa and Ashley (currently skilled lab technicians planning their next steps in life!), with minimal editing by me. They did some fantastic research in their senior year and put together this blog post to teach the world about menstrual cycling in young girls. It's worth a read, and please comment with your thoughts!

Adolescent Menstrual Variation and Oral Contraceptives
By: Theresa Emmerling, Ashley Higgins and Kathryn Clancy

Many informational videos and documentaries have been produced to inform young women on the changes that they will experience during puberty and upon first menstruation, also called menarche. Unfortunately, these explanations are quite often generalizations that can lead to misrepresentations of what is normal. The information available to young women today stresses normative values for menstrual cycle length rather than the wide degree of variation characteristic of their cycles and may have an impact on adolescents’ future choices concerning oral contraceptives.

Figure 1 from Vihko and Apter 1984

Most women are taught that the menstrual cycle is twenty-eight days long, with ovulation occurring at day 14, and that only tiny deviations from this are healthy. Teens are taught to expect that every month after first menses they will experience menstruation for about 5 days; however, most adolescents do not experience the average menstrual cycle. Many adolescents experience longer menstrual cycles, with the luteal phase lasting anywhere between four to thirteen days (Apter, 1978), and anovulation, where an egg is not released from the ovary, is the primary characteristic of their cycles (Figure 1, Vihko and Apter 1984). The HPO axis is not an “on/off” switch that commences a string of twenty-eight day menstrual cycles at menarche. Rather, it takes time for the pituitary to respond to LH surges, which occurs only after multiple exposures to GnRH and estrogen (Apter et al, 1978; Apter, 1997). Therefore, it can take an adolescent up to five years to begin seeing something closer to the average twenty-eight day cycle (Figures 1 and 2, Vihko and Apter 1984).

Figure 2 from Vihko and Apter 1984

To be fair, the challenge is determining what the normal variation in an adolescent’s cycle is and what is due to pathology: environmental factors and pathologies may influence the menstrual cycle during development of the HPO axis. Numerous studies have tried to pathologize what we believe is normal variation in adolescent menstrual cycles, calling them “menstrual disturbances” or characterizing them as some level of amenorrhea (Morimatsu et al, 2009). As of yet, there is no conclusive evidence. Many studies find correlations between irregular menstrual cycles and pathology (Singer et al, 2009), but do not control for oral contraceptives (i.e., van Hoof et al, 2004), other environmental factors that may influence the HPO axis (Christo et al, 2008), or the study consists of adolescents with an already known pathology (El-Khayat, 2008). The American Academy of Pediatrics published a paper in 2006 stating that while the definition of amenorrhea is the absence of menses for six or more months, adolescents should be examined after only three months and "not reassured that it is 'normal' to have irregular periods in the first gynecological years" (p. 2247).

Given that it is more common, even normal, for adolescents to have very long menstrual cycles, we are concerned with what looks like stronger criteria for amenorrhea in exactly the population where it is expected (though the AAP paper discusses the low frequency of very long cycles, it also fails to mention the frequency of the pathology they worry is hidden in these long cycles). Further, more stringent criteria that misrepresents normal variation in this group of women serves only to frighten a population already concerned about normality and fitting in. For many, the teenage years are a time when standing out is to be avoided, and anything that makes one seem abnormal – an early or late age at menarche, long or short menstrual cycles – can be a stigma and cause stress. Educating young women on the reality, that this variation is what is normal, and that if anything the 28-day cycle is abnormal at this life stage, may prevent some of the considerable misunderstandings they have about their health. Understanding one's own body is an important step in making educated, healthy choices in the future. If most young women do not actually experience what they are taught is the average menstrual cycle, despite the fact that the reality is that wide variation in menstrual cycle length is the primary characteristic of post-menarcheal cycling, we are providing information that could lead them to feel abnormal and want to treat what is likely healthy variation.

A source of serious concern stems from what’s happening in the doctor’s office. Doctors, particularly in the United States, prescribe oral contraceptives at the slightest mention of deviation from the norm or evidence of a “menstrual disturbance.” In 79% of cases, health care providers will prescribe OCs at the patient’s request (Andrista et al, 2004). Less than 5% of doctors offer alternative forms of contraception to their patients in the US (Gerschultz, 2007), despite the fact that intrauterine devices, or IUDs, are more widely prescribed globally, and are both safe and effective. Future research questions should address whether doctors believe OCs are the best choice for women or that they the easiest method to prescribe; further, it is important to understand the decisions involved in prescribing these hormone treatments to adolescents. We have found evidence of doctors prescribing oral contraceptives to girls as young as twelve years of age (Cromer et al., 2008). Additionally, doctors prescribe OCs for adolescents who do not “live a lifestyle conducive to menstruation” (Sucato, 2002). We worry that ingesting cocktails of exogenous hormones have become a tool of convenience without regard to the possible trade-offs in their consumption. There is a large gap in the literature concerning adolescents and the long-term effects of OCs, yet doctors’ primary concern is that adolescents will accidentally skip a couple pills every pack (Omar et al, 2005).

Natural variation in adolescent hormone levels is a largely unexplored realm of science, with the same handful of decades-old articles cited repeatedly. Further research will yield not only a better understanding of this "time of change" but also less pathologizing of natural variation. However, until that research is published and generally accepted in the scientific and medical communities, the prescription of OCs for adolescents should weighted against the possible long-term impacts of priming an immature HPO axis with hormones.

References

American Academy of Pediatrics Committee on Adolescence, American College of Obstetricians and Gynecologists Committee on Adolescent Health Care, Diaz A, Laufer MR, & Breech LL (2006). Menstruation in girls and adolescents: using the menstrual cycle as a vital sign. Pediatrics, 118 (5), 2245-50 PMID: 17079600

Andrist LC, Arias RD, Nucatola D, Kaunitz AM, Musselman BL, Reiter S, Boulanger J, Dominguez L, & Emmert S (2004). Women's and providers' attitudes toward menstrual suppression with extended use of oral contraceptives. Contraception, 70 (5), 359-63 PMID: 15504373

Apter, D, Viinikka, L, Vihko, R. (1978). Hormonal pattern of adolescent menstrual cycles. J of Clin Endocrinol Metab 47: 944-954.

APTER, D. (1997). Development of the Hypothalamic-Pituitary-Ovarian Axis Annals of the New York Academy of Sciences, 816 (1 Adolescent Gy), 9-21 DOI: 10.1111/j.1749-6632.1997.tb52125.x

Christo, K., Cord, J., Mendes, N., Miller, K., Goldstein, M., Klibanski, A., & Misra, M. (2008). Acylated ghrelin and leptin in adolescent athletes with amenorrhea, eumenorrheic athletes and controls: a cross-sectional study Clinical Endocrinology, 69 (4), 628-633 DOI: 10.1111/j.1365-2265.2008.03237.x

Cromer BA, Bonny AE, Stager M, Lazebnik R, Rome E, Ziegler J, Camlin-Shingler K, & Secic M (2008). Bone mineral density in adolescent females using injectable or oral contraceptives: a 24-month prospective study. Fertility and sterility, 90 (6), 2060-7 PMID: 18222431

El-Khayat, H., Soliman, N., Tomoum, H., Omran, M., El-Wakad, A., & Shatla, R. (2008). Reproductive hormonal changes and catamenial pattern in adolescent females with epilepsy Epilepsia, 49 (9), 1619-1626 DOI: 10.1111/j.1528-1167.2008.01622.x

GERSCHULTZ, K., SUCATO, G., HENNON, T., MURRAY, P., & GOLD, M. (2007). Extended Cycling of Combined Hormonal Contraceptives in Adolescents: Physician Views and Prescribing Practices Journal of Adolescent Health, 40 (2), 151-157 DOI: 10.1016/j.jadohealth.2006.09.013

Morimatsu, Y., Matsubara, S., Watanabe, T., Hashimoto, Y., Matsui, T., Asada, K., & Suzuki, M. (2009). Future recovery of the normal menstrual cycle in adolescent patients with secondary amenorrhea Journal of Obstetrics and Gynaecology Research, 35 (3), 545-550 DOI: 10.1111/j.1447-0756.2009.01014.x

Omar H, Kives S, & Allen L (2005). Extended use of the oral contraceptive pill--is it an acceptable option for the adolescent? Journal of pediatric and adolescent gynecology, 18 (4), 285-8 PMID: 16171734

Singer, K., Rosenthal, A., & Kasa-Vubu, J. (2009). Elevated Testosterone and Hypergonadotropism in Active Adolescents of Normal Weight with Oligomenorrhea Journal of Pediatric and Adolescent Gynecology, 22 (5), 323-327 DOI: 10.1016/j.jpag.2008.12.010