Gestational diabetes and metformin-Is that the best that medical thinking has to offer?

Gestational diabetes or elevated blood sugar is often treated with metformin to improve blood sugar levels and considered the standard approach to treating gestational diabetes. The research suggests that it has little negative effects on the pregnant mother. However, does significant risks to both mother and baby if the incidence of premature birth count? Here are a few aspects to consider regarding the use of metformin to control blood sugar during pregnancy.

A study of patients receiving a dose of metformin, combination of Clomiphene citrate (CC) and metformin both faired better than CC alone for the induction of ovulation (Neveu, Granger, St-Michel, & Lavoie, 2007).  As the combined group showed no benefit compared to metformin alone, one might consider that metformin alone may be considered for the positive effects.

In another study metformin and diet interventions showed a significant outcome compared to non-metformin-diet interventions. The metformin diet showed a reduction of 14 adverse events in a group of 76 expectant mothers, compared to the non-treated group of 36 adverse events out of 76 pregnancies (Glueck et al., 2013).

Thatcher and Jackson (Thatcher & Jackson, 2006) compared pregnancies of 188 women. 61 experienced miscarriages and 11 of those had stopped taking metformin, suggesting other abnormalities beyond metformin’s actions. 81% of women with pregnancies before metformin, 67% had prior miscarriages. 37% of these also miscarried again. Whilst metformin appeared to show minimal effects to mother and foetus 22% were born prematurely.

Whilst metformin has shown favourable outcomes in PCOS states, questions around pertinent biological mechanisms should warrant further discussion. It’s well known that two key endocrine actions may be compromised during the failure to achieve full gestation. Estrogen induces hypoxia in the uterus (Peat, 1997) and failure to produce adequate progesterone to counter the effects of estrogen may be implicated in the commonly fragile time around weeks 9-10 of pregnancy and incidence of miscarriage.

A concern of metformin are its affect transplacentally. Metformin appears to influence testicular size in males and affects sertoli cells. In females it may also lead to decreased androgen synthesis. Birth weight percentile is also significantly lower in pregnancies treated with metformin (Bertoldo, Faure, Dupont, & Froment, 2014)I Metformin has generally appeared safe in expecting mothers but considerable concern should be made regarding its long term effects to offspring and development most notably to reproductive tissues.

Hypothyroidism is a key factor in maintenance of pregnancy and alongside progesterone, thyroid hormone deficiency can be implicated in poor cellular energetics, production of adenosine tri phosphate (ATP) and blood sugar regulation. There remains much debate about the issue of subclinical hypothyroidism, values and when to treat and perhaps metformin’s role despite showing some promises may be treating a symptom related to insulin sensitivity. Failure

So perhaps these questions might be more pertinent before prescribing an agent that shows potentially negative effects to the fetus?

  1. What is the nutrition of the mother, is it enough and does it contain enough nutrients to enhance/maintain adequate progesterone/thyroid production?
  2. Is estrogen increasing at a rate that suppresses progesterone/thyroid levels and persistently decreases insulin sensitivity?
  3. Is there enough carbohydrate in the diet to ensure that carbohydrate is effectively utilised instead of persistent conversion of fats, increasing overall stress to both mother and fetus?
  4. Are the values of hypothyroidism and the identification of subclinical/functional hypothyroid factors appropriate?
  5. Is gestational diabetes a reflection of the above points?

The use of metformin, without questioning these mechanisms, remains at best a reduced treatment that fails to address a range of biological interactions and function.


Bertoldo, M. J., Faure, M., Dupont, J., & Froment, P. (2014). Impact of metformin on reproductive tissues: an overview from gametogenesis to gestation. Annals of Translational Medicine2(6), 55.

Glueck, C. J., Goldenberg, N., Pranikoff, J., Khan, Z., Padda, J., & Wang, P. (2013). Effects of metformin-diet intervention before and throughout pregnancy on obstetric and neonatal outcomes in patients with polycystic ovary syndrome. Current Medical Research and Opinion29(1), 55–62.

Neveu, N., Granger, L., St-Michel, P., & Lavoie, H. B. (2007). Comparison of clomiphene citrate, metformin, or the combination of both for first-line ovulation induction and achievement of pregnancy in 154 women with polycystic ovary syndrome. Fertility and Sterility87(1), 113–120.

Peat, R. (1997). From PMS to Menopause: Female Hormones in context.

Thatcher, S. S., & Jackson, E. M. (2006). Pregnancy outcome in infertile patients with polycystic ovary syndrome who were treated with metformin. Fertility and Sterility85(4), 1002–1009.

What is functional hypothyroidism?

You won’t find the term functional hypothyroidism in the medical literature, or at least not yet. Primarily due to clinical hypothyroidism being bound to a rigid assessment usually diagnosed by the blood test thyroid stimulating hormone or TSH.

TSH secretion is controlled by synthesis of thyroid releasing hormone or TRH in the supraortic and supraventricular nuclei of the hypothalamus. TRH is transported to the anterior pituitary by the hypothalamo- hypophysial portal system where it stimulates synthesis of TSH. T4, T3 and TRH control the secretion of TSH (Gardner et al., 2011).

TSH production can also be affected by TSH receptor damage, medical drugs, disease states, iodide, blood glucose levels and other circulating hormones TSH may also be affected by environmental pollutants and heavy metals (Llop et al., 2015).  Metabolic disease and increases in Body Mass Index appear to be correlated with an increase in TSH levels (Ruhla et al., 2010).

Often, you will see clear links and studies to key micronutrients such as zinc, selenium, iodine and other important co-factors. These deficiencies can exist demographically but usually in westernised societies, there deficiency can be linked to impaired absorption rates, perhaps linked to digestive dysfunction and other factors.

“Measuring the amount of thyroid in the blood isn’t a good way to evaluate adequacy of thyroid function, since the response of tissues to the hormone can be suppressed (for example, by unsaturated fats) (Peat, R.1999).

 Dietary factors such as unsaturated fatty acids in the diet may potentially be one of the most overlooked factors that supress thyroid function. Other factors such as caloric restriction, stressful environments, over exercising and other factors are some of the others. It’s well known that in certain areas of hormone dysregulation such as menstrual cycle irregularities, oligoamenorrohea (loss of cycle), anovulation (failure to ovulate) and lack of libido and fertility in both men and women,  can be attributed to poor energy intake and environmental factors (Nieuwenhuijsen et al., 2014) (Skakkebæk, 2003). Dietary factors have synergy with hormonal imbalances perpetuating high levels of estrogen.

The functional suppression of thyroid function by unsaturated fats, eating a so-called healthy diet (full of uncooked brassica vegetables, nuts and seeds) orthorexic states and other factors is largely ignored by physicians.

I can say with some certainty, after completing postgraduate studies at university with a number of Doctors, that diet and inhibitory factors of diet rarely get assessed when it comes to assessing energy and thyroid function.

A persistent functional hypothyroid state, induced by unsaturated fats may lead to the pre-diabetic and diabetic states induced by an inability to utilise carbohydrate and the preferential shift to use of fats instead of sugars as suggested in the Randle or glucose fatty acid cycle (Randle, Garland, Hales, & Newsholme, 1963). Increased cortisol, oxidation, decreased carbon dioxide and an increased stress on the oxidative system, could potentially lead to glycolysis and an increase in lactic acid, further increasing damage, stress and further suppression of thyroid function.

Measurement of thyroid blood tests remains inaccurate and problematic without the inclusion of a variety of symptoms and previously accurate assessment, such as basal metabolic rate, body temperature and pulse. The suppression of both thyroid and adequate energy states will always remain.

As the common approach for diagnosing hypothyroidism is having TSH above 4 or 5 mmUL and the preferred treatment is to supplement with synthetic levothyroxine. How much change can you realistically achieve if you fail to address the supressed metabolism induced by diet, an individuals susceptibility to stress and their own environment?



Gardner, D. G., Shoback, D. M., Greenspan, F. S. et al .(2011). Greenspan’s Basic and Clinical Endocrinology. McGraw Hill.

Llop, S., Lopez-Espinosa, M. J., Murcia, M., Alvarez-Pedrerol, M., Vioque, J., Aguinagalde, X., … Ballester, F. (2015). Synergism between exposure to mercury and use of iodine supplements on thyroid hormones in pregnant women. Environmental Research, 138, 298–305.

Nieuwenhuijsen, M. J., Basagana, X., Dadvand, P., Martinez, D., Cirach, M., Beelen, R., & Jacquemin, B. (2014). Air pollution and human fertility rates. Environment International, 70, 9–14.; 10.1016/j.envint.2014.05.005

Peat, R. (1999). Thyroid Therapies, Confusion and Fraud. Retrieved from

Randle, P. J., Garland, P. B., Hales, C. N., & Newsholme, E. A. (1963). The glucose fatty-acid cycle its role in insulin sensitivity and the metabolic disturbances of diabetes mellitus. The Lancet, 281(7285), 785–789.

Ruhla, S., Weickert, M. O., Arafat, A. M., Osterhoff, M., Isken, F., Spranger, J., … Möhlig, M. (2010). A high normal TSH is associated with the metabolic syndrome. Clinical Endocrinology, 72(5), 696–701.

Skakkebæk, N. E. (2003). Testicular dysgenesis syndrome. In Hormone Research (Vol. 60, p. 49).