HPO axis
A rapid increase in which hormone causes ovulation?
LH
What are the two forms of thyroid hormone?
Thyroxine (T4) and triiodothyronine (T3)
What are the main presentations in AFAB of hypothyroidism?
Heavy menstrual bleeding with irregular cycles, weight gain (hyperprolactinaemia, lowered metabolism), fatigue, cold intolerance, hair loss
What are the main presentations in AFAB of hyperthyroidism?
Infrequent or no periods, heat intolerance, weight loss, anxiety, infertility
Lack of which hormones triggers endometrial shedding and menstrual bleeding normally?
Oestrogen and progesterone
What is the only positive feedback mechanism in the hypothalamic-pituitary-thyroid axis?
How does hypothyroidism lead to annovulation?
Increased TRH increases prolactin which decreases GnRH.
Decreased GnRH decreases LH and FSH
Basal metabolic rate is increased so even though you eat more your metabolism is burning body fat and calories at a faster rate.
Which hormones control the luteal phase?
Drop in oestrogen and rapid increase in progesterone
When could TSH results be misleading in thyroid dysfunction?
Secondary hypothyroidism (pituitary gland does not increase TSH despite low T3/T4).
Drugs affecting pituitary function can depress TSH independent of thyroid function.
How do SHBG levels change in hypothyroidism and what effect does this have on menstrual bleeding?
Decreased SHBG = increased free oestrogen = heavy bleeding
Which autoimmune disease is the most common form of hyperthyroidism, and what are the effectors called?
Graves disease, thyroid stimulating immunoglobulins